Load control for gas turbine plant

ABSTRACT

In a load regulating device for a gas turbine plant, which comprises in a flow-path for the working medium a compressor, heater and turbine in succession, the improvement, that at least one by-pass conduit having a flow-regulating element is provided, which by-pass conduit branches off the flow path at a point situated in the direction of flow of the working medium after a stage group of the compressor and in front of the heater, and opens into the flow path at a point situated between two stage groups of the turbine; this load-regulating device allowing good part-load efficiency.

United States Patent Frutschi [54] LOAD CONTROL FOR GAS TURBINE PLANT [72] Inventor: Hans Ulrich Frutschi, Zurich, Switzerland 22 Filed: July 6,1971

21 Appl.No.: 159,650

[30] Foreign Application Priority Data FOREIGN PATENTS OR APPLICATIONS 354,470 7/1961 Switzerland ..60/59 T 550,943 2/1943 Great Britain ..60/59 T 566,337 12/1944 Great Britain ..60/59 T 862,385 3/1961 Great Britain ..60/59 Primary Examiner-Martin P. Schwadron Assistant Examiner-Harold Burks, Sr. Attorney-Austin P. Dodge et al.

[5 7] ABSTRACT In a load regulating device for a gas turbine plant, whichv comprises in a flow-path for the working medium a compressor, heater and turbine in succession, the improvement, that at least one by-pass conduit having a flow-regulating element is provided, which by-pass conduit branches off the flow path at a point situated in the direction of flow of the working medium after a stage group of the compressor and in front of the heater, and opens into the flow path at a point situated between two stage groups of the turbine; this load-regulating device allowing good part-load efficiency.

7 Claims, 4 Drawing Figures PATENTED 24 W 3 6 99 .681

sum 1 or 2 INVENTOR Hans U/ric/i FruLsc/nl ATTORNEYS PATENTEDnm 24 m2 SHEET 2 OF 2 Ill-l m m T W M 0 W m n M w E6 0 S w m Q m H F 2 2 x 5 1 f 1 My All LOAD CONTROL FOR GAS TURBINE PLANT BACKGROUND OF THE INVENTION The invention relates to a load regulating device for a gas-turbine plant having a compressor, heater and turbine in succession in the path of flow of the working medium.

In full-load operation, such gas-turbine plants function with a certain efficiency. The problem now arises of maintaining this efficiency as far as possible also in part-load operation. In known gasturbine plants having an open circuit, the perfonnance is regulated by temperature regulation at the turbine plant. In known plants with a closed circuit, filling-quantity or pressure level regulation is used. In gas-turbine plants, it is furthermore known to provide, for rapid load reductions, a return conduit by which the working medium compressed in the compressor can be returned to the compressor inlet.

Whereas in the case of gas turbines having two or more shafts and a recuperator, temperature regulation provides fairly good part-load efficiencies, and pressure regulation gives a practically constant efficiency for any power, regulation by means of a return conduit gives poorer part-load efficiencies.

Of the regulating methods with more favorable partload efficiency, temperature regulation has the disadvantage that in the case of load variations, different expansions of the machine parts occur, which has an unfavorable effect, especially in the case where nuclear reactors are used as heaters. Pressure-level regulation does indeed permit the temperature in the circuit to be kept constant, but demands considerable expenditure for the working medium accumulator and transfer compressor.

SUMMARY OF THE INVENTION The problem underlying the invention is to obviate the enumerated disadvantages of the known plants and to attain, by substantially simpler means a good efficiency in the part-load range. In accordance with the invention, this problem is solved in that at least one bypass conduit having a flow regulating element is provided, which by-pass conduit branches off the flow path of the working medium at a point situated, in the direction of flow, after a stage group of the compressor and before the heater, and opens into the path of flow at a point situated between two stage groups of the turbine.

A particularly advantageous embodiment of the invention which ensures good load efficiencies down to 50 percent part load, is provided by branching the bypass conduit off the flow path at a point situated between the compressor and the heater.

Very good efficiencies can be obtained in practically all part-load ranges by providing two by-pass conduits having a flow regulating element, of which conduits the first is branched off the flow path at a point situated between the compressor and the heater, and the second branches off at a point situated between two stage groups of the compressor. For this particularly favorable embodiment of the invention, a control device is provided which, in the upper load range, regulates by means of the flow-regulating member of the first bypass conduit, but in the lower load range regulates by means of the flow rate regulating member of the second by-pass conduit while avoiding the compressor pumping limit.

If advantageously in the embodiment of the invention applied to gas-turbine plants with closed circuit, the part of the flow path of the gas-turbine plant leading from the exit of the turbine to the inlet of the compressor is made so large that the mass of the part of the working medium under lower pressure is greater than the mass of the part under higher pressure, pratically the same good efficiency behavior over the part-load ranges can be obtained in plants with closed circuit as in plants with open circuit.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTS The gas-turbine plant shown in FIG. 1 has a compressor 1, heater 2 and turbine 3, which is subdivided into two stage groups 3 and 3 The stage group 3 of the turbine 3 drives the compressor 1, the stage group 3 drives a generator 4. A flow path for the working medium of the gas-turbine plant is shown at 5. The working medium leaving at the stage group 3 of the turbine 3 gives off heat in a recuperator 6 to the working medium leaving the compressor 1. A cooler 7 is connected in front of the compressor 1. A return conduit 9 provided with a valve 8 leads from a point between two stage groups of the compressor back to the compressor inlet.

According to the invention, the gas-turbine plant has a by-pass conduit 11 which is provided with a flowregulating element 10, and which branches off the flow path 5 at'a point 12 situated, in the direction of flow, after a stage group of the compressor 1 and before the heater 2, and opens into the flow path 5 at a point 13 situated between the two stage groups 3 and 3 of the turbine.

If the gas-turbine plant is to operate with part load, the flow regulating element 10 is operated. Whereas the flow-regulating element 10 is fully closed in the case of full load, it is fully open in the case of half load and allows about 10 percent of the working medium quantity to flow in the by-pass to the heater 2 and to the stage group 3 of the turbine 3 through the by-pass conduit 11. In this way, the good efficiency attained in fullload operation can be practically maintained down to half load. The known return conduit 9, provided with the valve 8, in association with a likewise known bypass 18 for the stage group 3 of the turbine 3, serves for quick relief of the load.

The good part-load efficiency behavior follows from the three following reasons. The mass flow of working medium flowing through the heater 2 and the stage group 3 of the turbine 3 is regulated by the by-pass 10,11 in accordance with the amount of power required. The speed of the compressor 1 is reduced, whereby the inlet pressure of the turbine 3 and its expansion ratio are reduced. Whereas the part of the mass flow to be heated in the heater 2 falls approximately in proportion to the pressure at the inlet of the turbine 3, the part of the mass flow led through the bypass conduit 11 is utilized in the stage group 3 of turbine 3.

Whereas the plant shown in FIG. 1 is a closed gasturbine plant, the plant illustrated in FIG. 2 concerns an open gas turbine. The plant according to FIG. 2 differs from that according to FIG. 1 furthermore in that the compressor 1 and the two stage groups 3 and 3 of the turbine 3 are situated on one shaft in common. This common shaft drives a propeller 14. The common shaft for the two stage groups 3 and 3 of turbine 3 is here possible since the speed of the propeller 14 is reduced as the load falls. Similar conditions also occur in the case of pumps or compressors driven by the gas turbine.

The embodiment of a gas-turbine plant illustrated in FIG. 3 is more particularly suitable for plants which have still to be driven with very good efficiency even in the range below half load. There are provided two bypass conduits each having a flow-regulating element, namely a by-pass conduit 11 provided with a flow regulating element and a by-pass conduit 11 provided with a flow-regulating element 10 The first bypass conduit 11 branches off the flow path 5 (as in the embodiment examples according to FIG. 1 and 2) at a point 12 situated between the compressor 1 and the heater 2, i.e., after the recuperator 6. The second bypass conduit 11 branches off the flow path 5 at a point 15 situated between two stage groups 1 and l of the compressor 1. The two by-pass conduits 11 and 11 then open into the flow path 5 again respectively at points 13 and 13 situated between two stage groups of the turbine 3, the point 13 lying between the two stage groups 3 and 3 and the point 13 between two stages of the stage group 3 There is further provided a control device 16 which in the upper load range (100 percent to 50 percent) regulates by means of the flow regulating element 10 of the first by-pass conduit 11, but in the lower range (50 percent and below) regulates by flow regulating element 10 of the second by-pass conduit 11 while avoiding pumping of the compressor 1. In this way, the desired optimum efficiency can be maintained down to the lowest load ranges. Furthermore, in the gas-turbine plant with closed circuit shown in FIG. 3, the part of the flow path 5 of gas-turbine plant leading from the outlet of the turbine 3 to the inlet of the compressor 1 is made so large that the mass of the part of the working medium under lower pressure is greater than the mass of the part under higher pressure. To make the difference between the said masses as large as possible, the part of the flow path 5 leading from the outlet of the turbine 3 to the inlet of the compressor 1 comprises a container 17 containing working madium.

The embodiment illustrated in FIG. 4 shows a solution in which, despite the wide range of load variations, the construction is of the simplest possible. The by-pass between the stage oups 3 and 3 of the turbine 3. About 20 percent 0 the working medium stream flows in the by-pass conduit 11 while by-passing the second stage group 1 of the compressor 1, the heater 2 and the first stage group 3 of the turbine 3. v

I claim:

1. A load-regulating device for a gas-turbine plant having a flow-path for the gaseous working medium and in said flow-path in the direction of flow of said working medium a compressor, a heater and a turbine; at least one by-pass conduit for said flow-path; said by-pass conduit having a flow-regulating element and said by-pass conduit branching from said flow-path at a point situated in the direction of flow of said working medium after astage of said compressor and in front of said heater, and opening into said flow-path at a point situated between two stages of said turbine.

2. A load-regulating device, according to claim 1, in which said by-pass conduit branches from said flowpath at a point situated between said compressor and said heater.

3. A load-regulating device, according to claim 1, in which said by-pass conduit branches from said flowpath at a point situated between two stages of said compressor.

4. A load-regulating device, according to claim 2, in which a second by-pass conduit is provided, having another regulating element; said second by-pass conduit branching from said flow-path at a point situated between two stages of said compressor, and opening into said flow-path at a point situated between two stages of said turbine.

5. A load-regulating device, according to claim 4, in which a control device is provided for said flow regulating element of said first by-pass conduit and for said other flow-regulating element of said second by-pass conduit; said control device opening in the upper load range of said gas-turbine plant, said flow-regulating element of said first by-pass conduit, and opening, in the lower load range of said gas-turbine plant, said other flow-regulating element of said second by-pass conduit.

6. A load-regulating device, according to claim 1, in which said flow path for said working medium forms a closed circuit; the part of said flow-path leading from the outlet of said turbine to the inlet of said compressor being made so large that the mass of the part of said working medium being under lower pressure is greater than the mass of the remaining part of said working medium being under higher pressure.

7. Load-regulating device, according to claim 6, in which the part of said flow path leading from the outlet of said turbine to the inlet of said compressor comprises a container containing part of said working medium. 

1. A load-regulating device for a gas-turbine plant having a flow-path for the gaseous working medium and in said flow-path in the direction of flow of said working medium - a compressor, a heater and a turbine; at least one by-pass conduit for said flowpath; said by-pass conduit having a flow-regulating element and said by-pass conduit branching from said flow-path at a point situated in the direction of flow of said working medium after a stage of said compressor and in front of said heater, and opening into said flow-patH at a point situated between two stages of said turbine.
 2. A load-regulating device, according to claim 1, in which said by-pass conduit branches from said flow-path at a point situated between said compressor and said heater.
 3. A load-regulating device, according to claim 1, in which said by-pass conduit branches from said flow-path at a point situated between two stages of said compressor.
 4. A load-regulating device, according to claim 2, in which a second by-pass conduit is provided, having another regulating element; said second by-pass conduit branching from said flow-path at a point situated between two stages of said compressor, and opening into said flow-path at a point situated between two stages of said turbine.
 5. A load-regulating device, according to claim 4, in which a control device is provided for said flow regulating element of said first by-pass conduit and for said other flow-regulating element of said second by-pass conduit; said control device opening in the upper load range of said gas-turbine plant, said flow-regulating element of said first by-pass conduit, and opening, in the lower load range of said gas-turbine plant, said other flow-regulating element of said second by-pass conduit.
 6. A load-regulating device, according to claim 1, in which said flow path for said working medium forms a closed circuit; the part of said flow-path leading from the outlet of said turbine to the inlet of said compressor being made so large that the mass of the part of said working medium being under lower pressure is greater than the mass of the remaining part of said working medium being under higher pressure.
 7. Load-regulating device, according to claim 6, in which the part of said flow path leading from the outlet of said turbine to the inlet of said compressor comprises a container containing part of said working medium. 